The company that makes the “uncola” is accused of telling an untruth in a new marketing campaign that touts 7UP as “100% natural.” The nonprofit Center for Science in the Public Interest (CSPI) will sue 7UP’s manufacturer, Cadbury Schweppes, unless the company drops the claim. Although the company removed several artificial ingredients from the drink, at least one remains: high fructose corn syrup.

Sunny new television ads for 7UP show cans of the drink being picked from fruit trees, or harvested from the ground, yet there is no fruit juice in 7UP. The narrator says it “tastes better than ever because we stripped out all the artificial stuff leaving just five all natural ingredients.” Besides carbonated water and high fructose corn syrup, the other three are citric acid, unspecified “natural flavors,” and potassium citrate. Though not any better or worse nutritionally than plain table sugar, high fructose corn syrup is spawned from a complex, multistep industrial process by which starch is extracted from corn and converted with acids or enzymes into glucose and fructose.

“Pretending that soda made with high fructose corn syrup is ‘all natural,’ is just plain old deception,” said CSPI executive director Michael F. Jacobson. “High fructose corn syrup isn’t something you could cook up from a bushel of corn in your kitchen, unless you happen to be equipped with centrifuges, hydroclones, ion-exchange columns, and buckets of enzymes.”

In a legal notice to Cadbury Schweppes executives, CSPI litigation director Steve Gardner wrote that the primary purpose of the suit would be to prohibit the company from describing any product with high fructose corn syrup as “natural,” and that CSPI would also seek restitution, corrective advertising, and attorneys’ fees. CSPI’s announcement comes a week after Cadbury, Coca-Cola, and PepsiCo agreed not to sell sugary soda in schools, thus avoiding a separate lawsuit CSPI and other parties intended to file.

The Food and Drug Administration does not have an official definition for “natural” foods. Nor does it take action to prevent food companies from calling the most obviously artificial ingredients “natural.” For example, CSPI once complained about Ben & Jerry’s “All Natural” ice creams, which variously included such obviously non-natural ingredients as hydrogenated oil, corn syrup, alkalized cocoa powder, and even “artificial flavors.” But FDA took no action other than sending CSPI a letter indicating that “natural” was “not among our current enforcement priorities.”

In March the Sugar Association, which represents cane and beet sugar producers, petitioned the FDA to define “natural.” While FDA has no definition, the U.S. Department of Agriculture allows only those meat and poultry products that have been minimally processed can be labeled as natural. CSPI wrote to the FDA in support of the Sugar Association’s petition and urged the agency to adopt a definition identical to USDA’s. That would mean that high fructose corn syrup, partially hydrogenated oils, and other ingredients that are more than minimally processed couldn’t be called natural.

“If the FDA were doing its job, perhaps a lawsuit wouldn’t be necessary,” said Gardner, who will work with Massachusetts attorney Ken Quat on a Cadbury Schweppes suit. “While this particular mislabeling doesn’t present much of a health threat, consumers and honest companies shouldn’t have to put up with dishonest claims in the marketplace. Happily, though, several states have excellent consumer protection laws that can be used to stop deceptive advertising.”

CSPI said it will consider other legal action against companies that use high fructose corn syrup in their ostensibly “all natural” products.